ISO 23552-1:2007

INTERNATIONAL ISO
STANDARD 23552-1
First edition
2007-10-15

Safety and control devices for gas and/or
oil burners and gas and/or oil
appliances — Particular requirements —
Part 1:
Fuel/air ratio controls, electronic type
Dispositifs de commande et de sécurité pour brûleurs à gaz et/ou à fioul
et pour appareils à gaz et/ou à fioul — Exigences particulières —
Partie 1: Dispositifs de régulation du rapport air/combustible de type
électronique




Reference number
ISO 23552-1:2007(E)
©
ISO 2007

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ISO 23552-1:2007(E)
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©  ISO 2007
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ISO 23552-1:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Classification. 3
5 Test conditions . 3
6 Construction. 4
7 Performance . 5
8 EMC/Electrical requirements. 10
9 Marking and installation. 12
Annex A (normative) Manufacturer's declaration for sensors, actuators and repeatability . 14
Annex B (normative) Special requirements for single position feedback potentiometers in
electromechanical actuators . 19
Annex C (normative) Specific regional requirements in Japan . 20
Bibliography . 21

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ISO 23552-1:2007(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 23552-1 was prepared by Technical Committee ISO/TC 161, Control and protective devices for gas and
oil burners and gas and oil burning appliances.
ISO 23552 consists of the following parts, under the general title Safety and control devices for gas and/or oil
burners and gas and/or oil appliances — Particular requirements:
⎯ Part 1: Fuel/air ratio controls, electronic type
Additional parts are planned.
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ISO 23552-1:2007(E)
Introduction
For electronic fuel/air ratio control systems, there are numerous solutions for specific applications in the
market. For this reason, ISO/TC 161 decided to draft an International Standard for type testing for closed-loop
fuel/air ratio control systems only.
This part of ISO 23552 does not override requirements of relevant appliance standards. It is the intention that
the safety of the appliance not be reduced by any normal or abnormal operation of the ERC described in this
part of ISO 23552.
In this part of ISO 23552, there is no classification, either by heat input or by applications.
The accuracy of actual fuel/air ratio is not specified as a fixed value.
This part of ISO 23552 specifies which parameters the manufacturer is required to declare and under what
conditions this declaration is considered fulfilled. These parameters relate to the fuel/air ratio control systems
rather than the combustion process.
This part of ISO 23552 does not include a standard test rig, however, the purpose of the tests is to verify the
manufacturer's declaration under the conditions required in this part of ISO 23552.
This part of ISO 23552 is expected to be used in conjunction with ISO 23550:2004. This part of ISO 23552
refers to clauses and subclauses of ISO 23550:2004 or to variations thereof by the qualifier “addition”,
“modification” or “replacement” in the corresponding element.

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INTERNATIONAL STANDARD ISO 23552-1:2007(E)

Safety and control devices for gas and/or oil burners and gas
and/or oil appliances — Particular requirements —
Part 1:
Fuel/air ratio controls, electronic type
1 Scope
This part of ISO 23552 specifies safety, construction and performance requirements for electronic fuel/air ratio
control systems intended for use with gas or oil burners and gas or oil burning appliances. It also describes
the test procedures for evaluating these requirements and specifies information necessary for installation and
use.
This part of ISO 23552 is applicable only to closed-loop fuel/air ratio controls (see 3.1) and does not
differentiate into classes by heat input.
This part of ISO 23552 applies to electronic fuel/air ratio control systems that can be tested independently or
as part of an appliance or as part of a burner.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 23550:2004, Safety and control devices for gas burners and gas-burning appliances — General
requirements
IEC 60068-2-6:1995, Environmental testing — Part 2: Tests — Test Fc: Vibration (sinusoidal)
IEC 60529:2001, Degrees of protection provided by enclosures (IP Code)
IEC 60730-1:2007, Automatic electrical controls for household and similar use — Part 1: General
requirements
IEC 60730-2-5:2004, Automatic electrical controls for household and similar use — Part 2-5: Particular
requirements for automatic electrical burner control systems




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ISO 23552-1:2007(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
electronic fuel/air ratio control
ERC
closed-loop modulating system consisting of the electronic control, actuating elements for the fuel flow and the
air flow as a minimum, and allocated feedback signal(s)
NOTE Figure 1 shows an example of different feedback alternatives. For details, see also Table 1.


Key
1 electronic control module 8 sensor fuel/air
2 air 9 system boundary of the ERC
3 fuel 10 sensor flame
4 actuator air 11 sensor flue gas
5 actuator fuel 12 combustion process
6 sensor air 13 burner control system
7 sensor fuel
Figure 1 — Example of an ERC configuration
3.2
electronic control module
electronic main control module incorporating all inputs and outputs for the controlling elements
3.3
actuator
device for controlling the amount of fuel or air
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ISO 23552-1:2007(E)
3.4
sensor
device that gives a signal related to a physical property to which it responds
3.5
combustion process
chemical reaction between fuel and air to produce heat
3.6
defined state
state with one of the following characteristics:
a) the system passively assumes a state in which the signal available at the output terminals ensures a safe
situation under all circumstances
b) the system actively executes a protective action causing it to shut down followed by a restart or a lock out
c) the system remains in operation, continuing to satisfy all safety-related functional requirements
3.7
fault reaction time
time between the occurrence of a fault and the reaching of a defined state by the ERC
3.8
safety shut-down
de-energization of the main fuel flow means as the result of the action of a limiter, a cut-out or the detection of
an internal fault of the system
3.9
lock-out
process in which the system goes into one of the conditions described in 3.9.1 or 3.9.2
3.9.1
non-volatile lock-out
safety shut-down condition of the system, such that a restart can be accomplished only by a manual reset of
the system and by no other means
3.9.2
volatile lock-out
safety shut-down condition of the system, such that a restart can be accomplished by either a manual reset of
the system or an interruption of the mains power and its subsequent restoration
3.10
abnormal operation
operation of the appliance under the effect of internal failures or under the effect of foreseeable influences
outside the specified operational conditions
4 Classification
There is no classification used in this standard.
5 Test conditions
Unless otherwise stated, the ERC shall be tested in the relevant situations such as standby, start-up, normal
operation and lock-out.
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ISO 23552-1:2007(E)
Unless otherwise stated, the practical assessment shall be carried out under the following conditions:
⎯ ambient temperature: 20 °C ± 5 °C;
⎯ relative humidity: between 40 % and 80 %;
⎯ at rated supply voltage and frequency.
Testing shall always be performed according to a test plan, which shall be included in the test report. The
relevant assessment criteria should be part of this test plan.
6 Construction
6.1 General
The ERC shall consist of at least two actuators and either two actuator sensors or a process sensor; see
Figure 1 and Table 1, which shall be considered together. It shall have continuous, self-checking modes that
can be relevant, e.g. operating mode, stand-by mode, start-up mode and shut down mode. The complete
system shall include the peripheral elements, e.g. servo motors, actuators, positional devices, sensors,
variable-speed controls for combustion air fans and combustion analysis feedback systems.
Table 1 — Acceptable feedback types
Actuator Device Feedback Output feedback
a
Position Speed Flow or ∆P Pressure
For air Valve X — X X
b
Fan — X X X
For fuel Valve X — X X
Pressure — — X X
regulator
c
— At least 2 feedbacks (1 gas, 1 air) required
a
A feedback signal that is directly related to the mechanical part of the actuator.
b
If a fan speed signal is used as means to control the air flow, proof of air flow may not rely on fan
rotation alone. A possible additional signal can be derived from an independent air-proving device
checked at least during start up.
c
Actuator feedbacks can also be the following from the process:
— ratio of the actual fuel/air mixture;
— ratio signal from the flame;
— signal from the flue gas.

6.2 Construction requirements
ISO 23550:2004; 6.2, shall apply with the addition of the following.
For components constructed of plastic material, aspects of the following apply:
⎯ dimensional stability;
⎯ flow characteristics of the material;
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ISO 23552-1:2007(E)
⎯ possible heat shrinkage;
⎯ durability.
They shall be considered with respect to the mechanical, chemical, thermal and environmental conditions of
the intended use.
6.3 Materials
ISO 23550:2004; 6.3.1 to 6.3.6, shall apply with the addition of 6.3.7.
6.3.1 Special requirements for electromechanical actuators with position feedback sensors
The actuator feedback sensor shall always represent the actual position of the controlling element. At least the
following aspects shall be considered.
⎯ The mechanical connection between the actuator and the actuator feedback sensor shall be of form
closure construction and ensure no slippage, e.g. use of form-fitting constructions.
⎯ Torsion of the connection between the sensor and the controlling element shall be minor in relation to the
position measured.
If an actuator consists of a separate actuating and controlling element, the non-slippage requirement shall be
fulfilled. Screws, pins and other components that are necessary to ensure no slippage shall be secured, e.g.
by a locking compound.
6.4 Gas connections
ISO 23550:2004; 6.4, shall apply.
7 Performance
7.1 Performance test
Replace ISO 23550:2004, 7.1, with 7.1.1 to 7.1.3.
7.1.1 At ambient temperature
The timings and sequence actions are measured in the delivered state. The ERC is connected and installed
according to the manufacturer's instructions.
The timings and sequence of actions shall conform to 7.6.3 and 7.6.4.
These tests shall be performed under normal conditions (see Clause 5)
⎯ at the manufacturer's declared rated voltage(s) or, if this is a range, at the lowest and highest rated
voltages;
⎯ at 85 % of the lowest declared rated voltage;
⎯ at 110 % of the highest declared rated voltage.
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ISO 23552-1:2007(E)
7.1.2 At lower temperature
The tests according to 7.1.1 shall be repeated at 0 °C or at the lowest declared ambient temperature when
this is lower than 0 °C.
7.1.3 At high temperature
The tests according to 7.1.1 shall be repeated at 60 °C or at the highest declared ambient temperature when
this is higher than 60 °C.
NOTE Specific regional requirements are given in Annex C.
7.2 Leak tightness
ISO 23550:2004, 7.2, is not applicable.
7.3 Torsion and bending
ISO 23550:2004, 7.3, is not applicable.
7.4 Rated flow rate
ISO 23550:2004, 7.4, shall apply.
7.5 Durability
ISO 23550:2004, 7.5, shall apply.
7.6 Functional requirements
7.6.1 General
The ERC shall control the fuel-to-air ratio in a manner so as not to cause any hazardous conditions.
It is for this reason that all aspects of an ERC shall be assessed as a complete closed-loop system. The
feedback signals of the ERC shall ensure that the predetermined control value has been obtained and is
adhered to.
Under conditions that can lead to abnormal operation, the ERC shall maintain a defined state.
If a single potentiometer is used for position feedback in an electromechanical actuator, it shall meet the
additional requirements listed in Annex B.
7.6.2 Burner control interface
The ERC shall be interfaced and interlocked with the burner control system in order to ensure that the
requirements of the burner control system according to IEC 60730-2-5 and this part of ISO 23552 are fully
maintained.
This may be achieved by internal or external interface.
Any interface and interlock between the ERC and burner control shall not degrade the safety of the complete
system.
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ISO 23552-1:2007(E)
7.6.3 Restart or lock-out after safety shut-down
If a restart follows a safety shut-down, the number and the interval of subsequent restarts shall comply with
the requirements of the application standard.
An automatic start-up attempt by a control function shall not override the safety shut-down conditions.
If lock-out follows a safety shut-down, the type of lock-out shall comply with the application standard.
7.6.4 Start-up sequence
The burner control system shall give control commands to the ERC regarding the start-up sequence. A fault
condition of the ERC shall result in a defined state.
7.6.5 Pre-set/predefined range
If the ERC operates outside the pre-set/predefined range for longer than as declared by the manufacturer, it
shall result in a defined state.
7.6.6 Accuracy requirements
The manufacturer shall declare the typical accuracy for the ERC; see Note 3.
For type testing, the following information shall be supplied:
a) applicable closed-loop (sensor, actuator and electronic control module; see Figure 1) methods as used in
the ERC;
b) relevant data of sensors and actuators, which shall be provided as part of the declared typical accuracy of
a closed loop; see Tables A.1 and A.2;
c) if more than one closed-loop method is used, the defined accuracy of each closed-loop method; see
Table A.3.
At least two (as for component failures) influences under normal operation shall be taken into consideration.
The results of the failure assessment shall be considered as well.
NOTE 1 Due to variations in technology and applications, it is not possible to give minimum quantitative accuracy
requirements for all possibilities.
NOTE 2 For calculation of the typical accuracy, the mean square value is recommended.
22 2
NOTE 3 The typical accuracy of the system, is ab++.n (the root of the sum of the squares), where a, b, ., n
( )
are the accuracies of the individual component, as shown in Annex A.
7.7 Endurance
7.7.1 General
All components of the control shall be able to withstand the tests as detailed in 7.7.2 and 7.7.3. If the control
function is an integral part of an apparatus, the long-term performance tests can be combined. The test of
7.7.2 and the test of 7.7.3 shall not be carried out on the same test sample.
In the case of the control not having a clear operating cycle, the long-term performance test shall be carried
out for the minimum specified amount of time.
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ISO 23552-1:2007(E)
7.7.2 Stress test
7.7.2.1 Thermal stress test
The thermal stress test shall be carried out with the terminals loaded with the loads and power factors as
declared by the manufacturer.
The purpose of the test is to expose the electronic components of the control to temperature cycles between
limits likely to be reached in normal use owing to fluctuations in ambient temperature, temperature variations
in the component itself, power-supply fluctuations and temperature changes, such as from standby to
operation and
...